Frequency changing apparatus and method



Feb. 26; 1946. KENT 2,395,744

FREQUENCY CHANGING APPARATUS AND METHOD Filed July 8, 1943 /EQ''IIIIII'i LOWFEE Ue-Ncr GENEIZHTO/E f2 (pm /4 /5 Patented Feb. 26, 1946FREQUENCY CHANGING APPARATUS AND METHOD Earle L. Kent, Elkhart, Ind.,assignor to. C. G. Conn, Ltd., Elkhart, Ind., a corporation of IndianaApplication July 8, 1943, Serial No. 493,888

4 Claims.

This invention relates to frequency changin apparatus and method andmore particularly to changing the frequency of electrical waves withoutchanging their shape or other characteristics.

One of the objects of the invention is to provide a frequency changingapparatus and method in which the frequency of a wave may be increasedor decreased without changing its shape.

Another object of the invention is to provide a frequency changingapparatus and method in which a pattern is produced according to theshape of an input wave and is scanned at a rate proportional to thedesired output frequency.

Still another object of the invention is to provide a frequency changingapparatus and method in which an annular pattern is produced by acathode ray apparatus and is scanned by a secand cathode ray at a rateproportional to the desired output frequency.

A still further object of the invention is to provide a double endedtube, one end producing a pattern and the other end scanning the patternto produce a Wave havingthe same shape as the input wave and any desiredfrequency.

The above and other objects and advantages Will be more readily seenwhen read in connection with the accompanying drawing, in which- Figure1 is a diagrammatic View of one form of apparatus embodying theinvention;

Figure 2 is a diagrammatic illustration of the pattern produced by theinput side of the appartus; and

Figure 3 is a diagrammatic view of the scanning pattern.

In carrying out the invention a pattern is produced which varies inintensity in accordance with the shape of an input wave which may be anelectrical wave, an audible wave or a supersonic wave of any desiredcharacter. The pattern is then scanned at a frequency which may varysubstantially from the input frequency to produce an output wave havingthe same shape and general characteristics as the input wave but Whosefrequency is changed to the desired value. The pattern may be a lightpattern produced from film or in any other desired manner but ispreferably produced by a cathode ray beam on a mosaic screen which iscapable of holding a charge and will be described herein in connectionwith an apparatus of this type.

The apparatus as shown in Figure 1 comprises a double ended tube ldivided in its central part by a double sided mosaic screen H made up ofa fine screen which serves to insulate tiny metallic plugs from eachother. Screens of this type have heretofore been used in other apparatusand will not be illustrated or described in detail herein.

A pattern is impressed on one side of the screen I I by a cathode raymechanism in one end of the tube including a cathode 12, a grid [3, afirst anode I4, a second anode l5, horizontal deflector plates l5 andvertical deflector plates IT. The second anode I5 is connected to acollector ring I8 adjacent the screen. The input wave which may bederived from any desired source is applied at I9 and is impressed on thesecond anode and collector ring to vary the velocity of the cathode raybeam in accordance with the wave shape. The horizontal deflector platesl6 are connected to a generator 2| which is so arranged as to applythereto an alternating voltage equal to A Sin 21rf1t and a similarvoltage is impressed on the vertical deflector plates by a generator 22which is equal to A cos 21rf1t While separate generators at 2| and 22have been shown it will be understood that the same generator might beused with suitable circuits to produce the desired function of thefundamental frequency. These two deflector plates will cause the beam tobe deflected to travel in a circle on the screen to produce a circularpattern thereon.

If the device were to be used only as a delay device, this pattern couldbe scanned from the opposite side of the screen by a second cathode raybeam traveling in a circle of the same radius and not more than onerevolution behind the first beam. However, if the frequency of the inputwave is to be changed a different type of pattern must be produced andfor this purpose the input cathode ray beam is biased by an alternatingvoltage causing it to travel radially back and forth in an annulus toform a pattern as shown in Figure 2. Preferably the biasing isaccomplished by providing a biasing ring 23 in the path of the beamhaving a central anode 24 and connected to a high frequency generator25. The generator 25 impresses a voltage on the biasing ring which isequal to sin 21rfzt where is is substantially in excess of f1. With thisconstruction the beam will move rapidly back and forth along radiallines and will travel relatively slowly around the annulus to produce apattern as indicated at 26 in Figure 2. Since the velocity of the beamis modulated in accordance with the shape of the input wave theintensity of the pattern will vary around the annulus in accordance withthe shape of the input wave.

The charge pattern impressed on the screen II by the cathode ray beam onthe input side of the tube is scanned by a cathode ray beam in theoutput side of the tube which is produced by a cathode 2'! controlled bya grid 28 and first and second anodes 29 and 3!. The output beam isdeflected by horizontal deflector plates 32 and vertical deflectorplates 33 supplied with alternating voltage from generators 34 and 35re;- spectively. The generator 34 supplies a voltage equal to cos 21rf3tand the generator 35 supplies an alternating frequency equal to sin27rf3t where is is the desired output frequency. The beam is biased by abiasing ring 36 having a center anode 3'! and supp-lied with a sawtoothWave of frequency It by a. generator 38. 'The frequency supplied by thegenerator 38 is less than the frequency of f3 and is preferably equalto. the frequency f1 so that the beam will be biased to travel in a,spiral pattern as indicated at 39 in Figure 3. A collector ring 4| isconnected to the grid of a amplifier tube 44 whose plate circuit isconnected across a resistance 45 to output terminals 46 as shown. As thecathode ray beam 'in the output side of the, tube travels in a spiralpath over the pattern 26' of the mosaic-screen II, the plugs in thescreen will be driven to equilibrium by secondary emission to cause avarying current between the screen and the collector ring 4!. Due to thespiral path of the beam it sweeps over a fresh part of the screen ineach revolution so that the'fre'quency is may, if desired, be greaterthan the frequency f1 and so that the variation in current between thescreen and the collector ring 4| will follow the pattern produced by theThe output wave at the terminals.

used in substantially any place where it is desired to change thefrequency of a Wave withou-t'altering its shape. For example, a musical.

tone of constant pitch may be impressed on the input side of the tube atI9 and may be taken out at the terminals 46 at a different frequencyproportional to the frequency is, If the fre-v quency is is supplied bya variable generating system through a keyboard or the like, any desiredtone could be produced having the qualities of the input wave. Anotherdesirable use is in the field of secret communication in whichfrequencies of an input wave could be multiplied or divided to becomeunintelligible and could later be multiplied or divided by the samenumber to restore the original wave. Various other applications willoccur to those skilled in the art.

While one embodiment of the invention has been shown and described indetail herein, it will be understood'that this is illustrative only andis not intended as a definition of the scope of the invention,references being had to the appended claims for this purpose.

What is claimed is:

1-. Th method of changing. the frequency of a wayewhich comprisesproducing from the wave an annular pattern varying in intensityannularly in accordance with the shape of the wave, and scanning thepattern in a spiral path at a rate proportional to the. desired outputfree qu noy.

2. The method of; changing the frequency 'of a wave; which comprisesdeflecting a focused cathode ray beam to travel in a circle, biasing thebeam at a high frequency to cause it totravelin closely spaced radiallines around the circle varying the effective intensity of the beam,

in accordance with the wave shape producing a charge pattern from thebeam, and: scanning the pattern at a, rate proportional to, the,desiredout put frequency.

3. Frequency changing apparatus. comprising a screen, means forproducing; on the, screen; an annular pattern varying, annularlyinintensityin accordance with the shape ofan inputv wave,

and means for scanning the pattern a, spiral path at a at pr p rtional;to the desired u o t; f equency,

4. Freque cych n in -appa atus compr sin a do bl ended tub ajdoublesdmosa o scr n in t nt al part of; the tu e m ans in one end of. thetube; to. d re t a. fo used cat ode, my

on one side of the, screen and to cause the ray to move over the screenin closely spaced radial lines in an annulus, means to vary the cfiectivintensity of the beam in accordance" with the. shape ofan input wave tovform an annular pattern on the screen, and cathode ray: means in theother end of the tube to scan the pattern in a spiral at a rateproportional tothe desired output frequency.

